(1) Field of the Invention
The present invention relates to a technology for stereoscopic video playback and especially to the allocation of a video stream on a recording medium.
(2) Description of the Related Art
For distribution of moving image contents, optical discs such as DVDs and Blu-ray discs (BDs) are widely used. BDs are with larger capacity compared with DVDs and thus capable of storing high quality video images. Specifically, for example, a DVD is capable of storing standard definition (SD) images at the resolution of 640×480 according to the VGA, and 720×480 according to the NTSC standard. In contrast, a BD is capable of storing high definition (HD) images at the maximum resolution of 1920×1080.
In recent years, there is an increasing number of movie theaters where customers can enjoy stereoscopic (which is also referred to as three-dimensional (3D)) video images. In response to this trend, developments of a technology are underway, the technology for storing 3D video images onto an optical disc without degrading high image quality. Here, the requirement to be satisfy is that 3D video images are recorded on optical discs in a manner to ensure compatibility with playback devices having only playback capability of two-dimensional (2D) video images (which is also referred to as monoscopic video images). Such a playback device is hereinafter referred to as “2D playback device”. Without the compatibility, it is necessary to produce two different optical discs per content, one to be used for 3D video playback and the other for 2D video playback. This would cause increase in cost. Accordingly, it is desirable to provide an optical disc storing 3D video images in a manner that a 2D playback device is allowed to execute 2D video playback and that a playback device supporting playback of both 2D and 3D video images (which is hereinafter referred to as “2D/3D playback device”) is allowed to execute both 2D and 3D video playback.
FIG. 59 is a schematic diagram illustrating the mechanism for ensuring the compatibility of an optical disc storing 3D video images with 2D playback devices (see Patent Document 1). An optical disc 2401 has a 2D/left-view AV (Audio Visual) stream file and a right-view AV stream file recorded thereon. The 2D/left-view AV stream contains a 2D/left-view stream. The 2D/left-view stream represents video images to be visible to the left eye of a viewer in stereoscopic playback and on the other hand, also allows the use in monoscopic playback. The right-view AV stream file contains a right-view stream. The right-view stream represents video images to be visible to the right eye of a viewer in stereoscopic playback. The video streams have the same frame rate but different presentation times shifted from each other by half a frame period. For example, when the frame rate of the video streams is 24 frames per second, the frames of the left- and right-view streams are alternately displayed every 1/48 second.
As shown in FIG. 59, the 2D/left-view and right-view AV stream files are divided into a plurality of extents 2402A-2402C and 2403A-2403C, respectively, in GOPs (group of pictures) on the optical disc 2401. That is, each extent contains at least one GOP. Furthermore, the extents 2402A-2402C of the 2D/left-view AV stream file and the extents 2403A-2403C of the right-view AV stream file are alternately arranged on a track 2401A of the optical disc 2401. Each two adjacent extents 2402A-2403A, 2402B-2403B and 2402C-2403C have the same length of playback time. Such an arrangement of extents is referred to as an interleaved arrangement. Groups of extents recorded in an interleaved arrangement on a recoding medium are used both in stereoscopic playback and monoscopic playback, as described below.
As shown in FIG. 59, a 2D playback device 2404 causes a 2D optical disc drive 2404A to sequentially read the extents 2402A-2402C of the 2D/left-view AV stream from the optical disc 2401 and a video decoder 2404B to sequentially decode the read extents into left-view frames 2406L. As a result, left views, i.e., 2D video images are played back on a display device 2407. Note that the arrangement of the extents 2402A-2402C on the optical disc 2401 is designed in view of the seek performance and the reading rate of the 2D optical disc drive 2401A so as to ensure seamless playback of the 2D/left-view AV stream file.
As shown in FIG. 59, a 2D/3D playback device 2405, when accepting the selection of 3D video playback from the optical disc 2401, causes a 3D optical disc drive 2405A to alternately read the 2D/left-view AV stream file and the right-view AV stream file extent by extent from the optical disc 2401, more specifically, in the order of the reference numbers 2402A, 2403A, 2402B, 2403B, 2402C, and 2403B. Of the read extents, those belonging to the 2D/left-view stream are supplied to a left video decoder 2405L, whereas those belonging to the right-view stream are supplied to a right-video decoder 2405R. The video decoders 2405L and 2405R alternately decode the received extents into video frames 2406L and 2406R, respectively. As a result, left and right video images are alternately displayed on a 3D display device 2408. In synchronization with the switching between left and right video images, 3D glasses 2409 cause the left and right lenses to opacify alternately. Through the 3D glasses 2409, the video images presented on the display device 2408 appear to be 3D video images.
As described above, the interleaved arrangement enables an optical disc having 3D video images to be used for both 2D video playback by a 2D playback device and 3D video playback by a 2D/3D playback device.